The present invention relates generally to the actuation of riveting and other tooling in the art of automatic fastening. The present invention also relates to automatic fastening apparatus including riveting apparatus.
Conventionally, riveting apparatus for airplane fuselages or wing panels and the like has been hydraulically-operated. An example of such hydraulic riveting apparatus is found in U.S. Pat. No. 5,060,362 to Birke et al, which is assigned to the assignee of the present invention and which is hereby incorporated herein by reference. However, other types of riveting apparatus such as pneumatic, electromagnetic, and roller screw have been suggested.
Pneumatic driven riveting apparatus, while typically small and hand-held, is very noisy and inefficient and difficult if not impossible to place under electronic control due to the compressibility of air.
The standard riveting apparatus for many years has been hydraulic. While hydraulic riveting apparatus has been considered quite effective and reliable, providing high linear forces for installing rivets, slugs and similar fasteners in workpieces, it has also been considered desirable that riveting apparatus be provided which is quieter, faster, and more repeatable while still having the effectiveness and reliability of hydraulic riveting apparatus.
U.S. Pat. No. 1,483,919 to Walker suggests a riveting machine which utilizes an electrically operated screw which rotates with the rotating element of the riveting motor, utilizing separate means for holding the screw against rotation during a riveting stroke and returning the screw to the starting point at the end of the riveting stroke. Walker also discusses a construction in which the screw is non-rotatable, the rotating element of the motor constituting a nut which is rotatable but held against movement in the axial direction. This actuating apparatus may not be able to generate the high forces which may be required for some riveting operations. Other art which may be of interest includes U.S. Pat. Nos. 434,677; 2,075,162; 2,342,089; and 5,404,633.
U.S. Pat. No. 5,491,372 and published International application no. PCT/US94/10232 (WO 95/08860) to Erhart, which, along with U.S. patent application Ser. No. 08/154,953 on which the International application claims priority, are hereby incorporated herein by reference, disclose an electrically powered linear actuator including an actuator assembly having an actuator rod and a thread engaging portion, a motor assembly having a stator, and a housing. The thread engaging portion of the actuator assembly is moved along the threaded extent of a cylinder on rotation thereof which cylinder functions as an armature drive cylinder. The stator is selectively energized to rotate the armature drive cylinder clockwise or counterclockwise to reciprocally move the thread engaging portion of the actuator assembly and an output shaft of the actuator. A closed-loop feedback control includes a servo-amplifier, controller, and master controller for the actuator.
Such a roller screw actuator, identified as a GS series inverted roller screw actuator, is marketed by Exlar Corporation of Chanhassen, Minn. for applications such as automated assembly, ball screw replacement, dispensers, hydraulic cylinder replacement, machine tools, pneumatic cylinder replacement, pressing, stamping, indexing stages, material cutting, precision grinders, automatic tool changers, chip and wafer handling, die cutters, formers, material handling, parts, clamping, etc. Another commercially available actuator, identified by Exlar as an FT series roller screw force tube actuator, utilizes a roller screw mounted inside a periscoping tube mechanism. Other companies such as GSA-Gewinde Satelliten Antriebe AG of Horriwil, Switzerland, INA Bearing Company, Inc. of Fort Mill, S.C., and SKF Transrol of France also provide planetary roller screws.
Riveting apparatus must be rugged and be able to apply the huge forces required for fastener upset on such workpieces as aircraft fuselages and wing panels. Thus, as previously mentioned riveting apparatus for many years has been principally hydraulic. If a non-hydraulic riveting apparatus is to become practical, it must be able to ruggedly and reliably apply such high fastener upset forces.
It is accordingly an object of the present invention to provide non-hydraulic riveting apparatus which is rugged and reliable, is able to apply the high fastener upset forces which are required, and has sufficient speed of operation, efficiency and durability.
It is another object of the present invention to provide such riveting apparatus which is quiet, safe, is easily maintained, has long life, and has quick turn-around time for repairs, yet is inexpensive and may be operated inexpensively.
It is considered desirable that the riveting apparatus be controllable throughout the entire fastener upset operation so that the apparatus may be applied to different fastener alloys and so that repeatability and uniformity rivet-to-rivet may be achieved.
It is therefore a further object of the present invention to provide non-hydraulic riveting apparatus which is controllable throughout the entire fastener upset operation.
It is yet another object of the present invention to successively perform different machining operations on a workpiece without having to provide such a riveting apparatus actuator for each tool.
In order to provide quiet, safe, effective, easily and quickly repairable, inexpensive, and reliable non-hydraulic riveting apparatus which can deliver the high upset forces, in accordance with the present invention, a planetary roller screw is provided for actuating the fastener upset tooling.
In order that precise control of the entire fastener upset operation may be obtained, in accordance with the present invention, a servo-controlled electric motor is provided for operating a screw or force tube actuator for a fastener upset tool.
In order that different machining operations may be performed on a workpiece without having to provide an actuator for each tool, in accordance with the present invention, the tools are engaged in turn by the actuator for performing riveting and other machining in succession.
The above and other objects, features, and advantages of the present invention will be apparent in the following detailed description of the preferred embodiment of the present invention when read in conjunction with the accompanying drawings wherein the same reference numerals denote the same or similar parts throughout the several views.